The overall objectives of the project are to define the mechanisms regulating the biogenesis of embryonic chick liver delta-aminolevulinate synthetase (ALA synthetase). The specific aims are to determine the subcellular sites of synthesis and processing of the precursor to the subunit of the enzyme, to define the site(s) of action of hemin in the repression of biogenesis of the enzyme, and to investigate the mechanism of transport of this enzyme from its site of synthesis to mitochondria. A major effort will be directed at characterizing and purifying the messenger RNA for the subunit of the enzyme.